Laser iridotomy including Nd: YAG, argon and Nd: YAG combined with argon was performed on 42 eyes of 25 chinchilla rabbits. The postoperative follow-up was 8 months. The histopathological changes of the irides at the sites of the various laser shots under light, transmission and scanning electron microscopic examinations were compared. The results show: (1) In regard to the Nd: YAG laser effect on the target tissue, the inherent elasticity of the tissue may play a more important role in curative effects of the therapy than the thickness of the tissue. (2) Every iris hole, < 200 microns in diameter, performed by Nd: YAG or < 450 microns, by argon or argon combined with Nd: YAG was closed by the first postoperative week. The histopathological findings demonstrate that the pigment epithelial proliferation and migration are more marked in the irides with argon laser iridotomy. (3) An insufficient coagulative burn of the argon laser may cause congestion of iris blood vessels and possibly, result in more severe bleeding during succedent Nd: YAG laser shots.